The present project combines cellular and computational techniques to explore the role of specific forms of synaptic plasticity in the modulation of information processing in a behaviorally relevant neural network. This project will include an in-depth analysis of short-term synaptic plasticity (STSP) at an identified class of inhibitory interneurons (L3Os) in the siphon-withdrawal reflex (SWR) in Aplysia, and the long-term modulation of this synaptic plasticity. Although STSP is present at synapses in both invertebrates and vertebrates, its behavioral role is not well understood and difficult to address in many systems. However, recent studies in our laboratory have begun to link short- and long-term plasticity at the L3O synapse to behavioral plasticity in the SWR. Thus, the SWR circuit is well suited for a functional examination of STSP and will provide insights into the role of STSP in other systems. Furthermore, the knowledge gained with this project will provide important predictions to expand our understanding of the neural circuitry that underlies adaptive behavior, a connection that is often difficult to make in more complex nervous systems but is essential to our understanding of the human brain.